The present invention is related to Japanese patent application No. Hei. 11-347541, filed Dec. 7, 1999; the contents of which are incorporated herein by reference.
The present invention relates to a detected signal processing device, and more particularly, to a detected signal processing device suitable for a rotating sensor that detects a rotational direction and a rotational speed of a rotor and outputting rotational direction signals different in waveform according to the rotational direction based on the result of detection with timing corresponding to the detected rotational speed.
A detected signal processing device for the rotating sensor is known as disclosed in JP-A No. H10-70524. This discloses a rotating sensor of a type or system wherein information other than a rotational speed, such as a rotational direction, self-diagnostic information is superimposed on a rotational pulse signal as binary data, and the generated signal is transmitted. In such a device, however, a binary data word corresponding to data is additionally provided between pulse signals indicative of a rotational speed. Thus, since the time interval between the pulse signals becomes short as the rotational speed becomes fast, a transmittable data length is limited.
When, for example, a pulse width (time) of a pulse signal, which constitutes a data word, is narrowed (shortened) to avoid it, the number of bits for the data word can be increased even at the same rotational speeds. When the numbers of bits for data words are set identical to each other, the upper limit of a detectable rotational speed can be increased.
However, the shortening of the pulse width in this way means nonresistance to noise upon a detecting operation. A trade-off relation is established between characteristics of the two. In either case, restraints are placed on a transmittable data word at high rpm.
The present invention has been made in view of the foregoing. An object of the present invention is to provide a detected signal processing device for a rotating sensor and a detected signal outputting method therefor, which are capable of reliably transmitting signals without restraints placed thereon due to a rotational speed and an adverse effect exerted thereon due to noise, even if a signal indicative of a rotational direction and other data are added to a signal indicative of the rotational speed.
Accordingly, in a first aspect of the invention, there is provided a detected signal processing device suitable for a rotating sensor. A determining means determines whether the rotational speed of a rotor reaches a predetermined rotational speed. Signal pattern generating means utilizes rotational direction signals in combination to thereby generate each transfer signal different from the rotational direction and rotational speed of the rotor as a signal pattern. Signal processing means outputs a signal generated by the signal pattern generating means with timing corresponding to the rotational speed when the signal generated by the signal pattern generating means exists, where it is determined by the determining means that the rotational speed of the rotor has reached the predetermined rotational speed.
Since the rotational direction does not change suddenly when the rotational speed reaches the predetermined rotational speed since the rotor starts rotating in either a normal rotational direction or a reverse rotational direction, the rotational direction can be regarded as being maintained even though the rotational direction signals are not output continuously. Further, if the state of the rotational direction is output as the rotational direction signals again when the rotational speed reaches a state where the rotor may be rotated in the reverse direction as the rotational speed is reduced, then the state of the rotation of the rotor can sufficiently be represented as a detected signal.
In such a state in which the rotational speed of the rotor reaches the predetermined rotational speed, the output of either one of signals corresponding to the direction of rotation thereof with the timing indicative of the rotational speed allows the recognition of the rotational speed. Therefore, the signal patterns generated by combining signals different in waveform corresponding to the rotational direction in plural form can be output as transfer signals.
Thus, the transfer signals other than the rotational speed and the rotational direction can be output using the rotational direction signals different in waveform at other than the rotational speed at which no change is considered to occur in the rotational direction of the rotor. Even when the rotational speed of the rotor becomes fast, the signal pattern for each transfer signal can sufficiently be recognized within a range in which the rotational direction signals can be recognized. Therefore, the transfer signal or pulse signal can reliably be output without placing restraints or the like on its pulse width and the number of pulses thereof as distinct from the case where another signal pattern is superimposed between the conventional pulse signals indicative of the rotational speeds and the result of superimposition is output.
According to another aspect of the invention, rotational direction signals different in waveform corresponding to a rotational direction are utilized in combination in plural form on condition that the rotational speed of a rotor reaches a predetermined rotational speed or higher to thereby generate each transfer signal different from the rotational direction and rotational speed of the rotor as a signal pattern. The generated signal is output with timing corresponding to the rotational speed. Thus, since the rotor is kept at the predetermined rotational speed and the rotational direction does not change in such a state, the transfer signal corresponding to the signal pattern generated by utilizing the different rotational direction signals in combination in plural form can be output as an alternative to the output thereof as each rotational direction signal. Thus, each transfer signal can be output with timing indicative of the rotational speed of the rotating sensor. Further, since the transfer signal can be recognized if the rotational direction signal can be recognized at this time, the transfer signal can reliably be output without being affected by the rotational speed.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.